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United States Patent |
5,598,270
|
Meisser
,   et al.
|
January 28, 1997
|
Sensor device and position determination process and their use for the
control of an insertion robot
Abstract
The sensor device includes a planar code carrier on one object, and on
another object, a scanning device for an angle of view for determining a
viewing direction lying therein, and also a computing circuit. A
photodetector detects an illumination density during the course of the
scanning of the angle of view according to the direction of light
incidence. On the code carrier there is arranged a rectangular code field
with its center line parallel to the scanning plane. The code field
includes at least two rectangular positioning fields and a rectangular
interfield lying in between. The positioning fields contain positional
information on the objects which can be evaluated by the scanning device.
In at least one interfield, the code includes at least one boundary line
obliquely intersecting the center line, the scanning of which boundary
line produces a distinct variation of the illumination density in
dependence on the direction of light incidence, which corresponds to a
viewing direction to be established. The interfield may be subdivided by a
diagonal line into two optically identical interfield regions or by a
boundary line diagonally into two optically different interfield regions,
and this configuration may be mirror-symmetrically duplicated.
Inventors:
|
Meisser; Claudio (Cham, CH);
Singeisen; Felix (Kriens, CH)
|
Assignee:
|
ESEC S.A. (Cham, CH)
|
Appl. No.:
|
190086 |
Filed:
|
June 6, 1994 |
PCT Filed:
|
May 21, 1993
|
PCT NO:
|
PCT/CH93/00132
|
371 Date:
|
June 6, 1994
|
102(e) Date:
|
June 6, 1994
|
PCT PUB.NO.:
|
WO93/24806 |
PCT PUB. Date:
|
December 9, 1993 |
Foreign Application Priority Data
Current U.S. Class: |
356/400; 235/470; 356/399; 356/620; 414/273; 901/47 |
Intern'l Class: |
G01B 011/00 |
Field of Search: |
356/399,400,401,375
414/273,274
901/47
250/548,555,559,561
235/470
|
References Cited
U.S. Patent Documents
4764668 | Aug., 1988 | Hayard | 235/470.
|
5303034 | Apr., 1994 | Carmichael et al. | 414/274.
|
Foreign Patent Documents |
3241510 | May., 1984 | DE.
| |
Other References
Namco brochure, LN110/120.
|
Primary Examiner: Gonzalez; Frank
Assistant Examiner: Kim; Robert
Attorney, Agent or Firm: Cushman Darby & Cushman, L.L.P.
Claims
What is claimed is:
1. A system for sensing the relative position of two mutually displaceable
objects, comprising:
an optical code provided in a code field of a substantially planar code
carrier arranged on one of said objects for displacement therewith;
an optical scanner having a field of view which extends throughout a
viewing angle relative to an optical center, the optical scanner being
equipped to detect illumination density and direction from said optical
center for reading said optical code; said scanner being arranged on the
other of said objects for displacement therewith;
an illuminator for causing light to become incident on said code field;
means for displacing at least one of said objects relative to the other of
said objects, and thereby causing light which has become incident on said
code field to become within said viewing angle and detectable by said
optical scanner;
said field being substantially rectangular, having a longitudinal
centerline and including a plurality of fields arranged in a series
extending along said centerline and including at least one substantially
positioning field arranged between two substantially rectangular
interfields;
said positioning field containing coded information about the position of
said positioning field with respect to a reference point on said one of
said objects and about the identity of one of said objects;
each said interfield including at least one boundary line between two areas
which, when illuminated by said illuminator, can cause differing
illumination density to be detected by said optical scanner, said boundary
line crossing said centerline at an oblique angle thereto; and
control means operatively interconnecting said optical scanner and said
displacing means, for mutually positioning said two objects so as to
provide a determined relative position, based on differing illuminator
density detected by said optical scanner as a result of illumination of
said boundary lines of said interfields by said illuminator.
2. The system of claim 1, wherein:
in each of said interfields, each respective said boundary line is a
diagonal line.
3. The system of claim 1, wherein:
in each of said interfields, there are two said boundary lines which are
oblique to said centerline and oppositely oblique relative to one another.
4. The system of claim 1, wherein:
each of said interfields is flanked by respective two said positioning
fields, for a total of at least three interfields and at least four said
positioning fields;
the coded information contained by said positioning fields being related in
a series which extends along said centerline.
5. The system of claim 1, wherein:
said one object is a processing line for electronic computer chips, and
said other object is a robot for acting on computer chips on said
processing line.
6. The system of claim 5, wherein:
said displacing means is operable for moving said robot in these mutually
orthogonal directions relative to said processing line.
7. An information-providing target for use in locating a mobile robot
relative to a station on an automated processing line, comprising:
a substrate mountable at a site corresponding to a station on the automated
processing line;
an information block comprising a series of groups of line patterns
extending in a given direction corresponding to a scanning direction of a
sensor;
said information block being affixed to said substrate;
said series of groups of line patterns being constituted by a plurality of
positioning fields alternating with a plurality of interfields;
each positioning field comprising a plurality of parallel straight lines
extending normal to said direction, within a notional rectangle, as to
have opposite line ends;
each interfield being located between a respective two of said positioning
fields and including at least one line extending obliquely relative to
said direction.
8. The target of claim 7, wherein:
said substrate is retro-reflective, and each said line is opaque.
9. The target of claim 7, wherein:
each said interfield comprises a single line extending diagonally between
opposite ends of respective most closely neighboring ones of said lines of
respective adjacent ones of said positioning fields; said single line
being disposed between two triangular non-lined areas which, together with
said single line, fill a respective notional rectangle.
10. The target of claim 7, wherein:
there are three said interfields.
11. The target of claim 7, wherein:
each said interfield comprises a pair of triangular forms sharing a
hypotenuse which extends diagonally between opposite ends of respective
most closely neighboring ones of said lines of two respective adjacent
ones of said positioning fields; one of said triangular forms having a
substantially different degree of light reflectivity or transmissivity
than the other.
12. The target of claim 7, wherein:
each said interfield comprises a chevron-shaped line composed of two line
segments which meet at an apex located intermediate, relative to said
direction, respective most closely neighboring ones of said lines of
respective adjacent ones of said positioning fields; said single line
being disposed in complementary alternation with these triangular
non-lined areas, which, together with said chevron-shaped line, fill a
respective notional rectangle.
13. The target of claim 7, wherein:
each said interfield comprises a series of three triangular areas,
including two flanking triangular areas and one central triangular area,
mutually bounded by a chevron-shaped interface and, together, filling a
respective notional rectangle; said central triangular area having a
substantially different degree of light reflectivity or transmissivity
than do said to flanking triangular areas.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sensor device for establishing the relative
position of two mutually displaceable objects, a method of automatically
determining a position of a displaceable robot with respect to an object
with the aid of the sensor device, and a use of the sensor device and an
application of the method for controlling a mounting robot for a line of
machines and/or devices, in particular for the automatic processing or
treatment of electronic chips.
2. Discussion of the Prior Art
FIG. 1 schematically shows in perspective a line of machines for the
automatic processing and/or of devices for the automatic treatment of
electronic chips according to the prior art.
FIG. 2 shows in a schematic side view selected elements of the installation
shown in FIG. 1 according to the prior art.
The journal "productronic 1/2-1991", page 112 and "European Semiconductor",
October 1990, disclose the line of machines schematically represented in
perspective in FIG. 1 for the automatic processing and of devices for the
automatic treatment of electronic chips. The machines B1-B4 are, for
example, "die bonders" and "wire bonders" for establishing electrical
connections on the chips, and the devices E1-E2 are, for example,
continuous furnaces for the curing of plastics and devices for the
intermediate storage of the chips. The chips to be processed or to be
treated are contained in magazines M when they are transported, fed to the
machines B1-B4 or devices E1-E2 and prepared therein for processing or
treatment and also for transporting away after the processing or
treatment.
The machines B1-B4 and devices E1-E2 are set up in series. Arranged behind
this series, with regard to the transport of the magazines, is a rail
device T, on which there runs a mounting robot R, which grips, moves,
positions and releases the magazines M as required.
In FIG. 2, the machine B1, the rail device T and the mounting robot R are
represented in a schematic side view. The mounting robot R travels
rectilinearly and horizontally on the rail device T. A gripper G for the
magazine M is supported movably on the mounting robot R by means of an
advancing carriage V and a lifting carriage H. The advancing carriage V is
movable on the mounting robot R horizontally and orthogonally to the rail
device T towards the machine BI and away from it. The lifting carriage H
is movable vertically on the advancing carriage V. Consequently, the
gripper G can be moved with three Cartesian degrees of freedom or
directions of movement with respect to the machine B1 in order to bring
the magazine M to the intended magazine position P1 or P2 at the machine
B1 and unload it there, or to grip it there and lead it away from there.
This entails the problem of automating the movements of the mounting robot
R.
The machines B1-B4 are namely set up, changed and adjusted in accordance
with the requirements of fabrication. The individual machines are then
admittedly aligned as well as possible at right angles to the rail device
T or to the running direction of the mounting robot R, but are not
mechanically connected directly and in a predetermined way to the rail
device T. The only common reference is the floor plane; moreover, the
machines M or their magazine positions P1-P2 may be arranged at various
non-standardized heights above the floor and at various non-standardized
distances from the rail device T. Under these circumstances, to automate
the movements of the mounting robot R it is necessary to make the mounting
robot R itself learn the magazine position P1-P2 and determine the
corresponding set position of the gripper G, otherwise the magazine
positions P1-P2 would have to be measured after each change and entered
into the control of the mounting robot R as a corresponding default value,
which would be extremely complex. To detect the magazine positions
concerned, sensor devices are necessary.
A sensor device which can be used for this is disclosed, for example, by
the brochure "LN110/120" of the Namco company. It essentially comprises a
laser as light source, a constantly rotating mirror, a photodetector and
an angle-reference detector, which are all integrated in a measuring
device, and also a retro-reflector and, if appropriate, code plates, which
are attached on an object, and a microprocessor, one of the functions of
which is that of a computing circuit. Using the constantly rotating
mirror, the laser beam periodically scans a predetermined angle of view.
The retro-reflector returns the laser beam to the photodetector. As long
as the laser beam scanning at a constant rate meets the retro-reflector,
the photodetector generates a retro-reflection pulse, the duration of
which is inversely proportional to the distance of the retro-reflector
from the photo-detector. The closer the retro-reflector is to the
photodetector, the greater the pulse duty factor of retro-reflection
duration to dark interval in a period of the scanning. On the other hand,
the angle-reference detector generates an angle-reference pulse with each
period of the scanning. If, during the course of scanning, the laser beam
reaches the retro-reflector, a retro-reflection pulse begins. The time
between the beginning of the angle-reference pulse and the beginning of
the retro-reflection pulse is directly proportional to the angular
position of the retro-reflector with respect to the direction of the laser
beam at the beginning of the angle-reference pulse. Consequently, the
angular position or the distance of the retro-reflector can be measured
contactlessly, provided that the dimension of the retro-reflector in the
plane of the scanning to the laser beam or orthogonally to the axis of the
rotating mirror is known. If the known retro-reflector is, furthermore,
arranged at a defined point of an object, or if a known object is arranged
between the known retro-reflector and the photodetector in such a way that
it interrupts the laser beam, the computing circuit can calculate the
distance and position of the object on the same principle. In this case,
there may be arranged on the object additional code plates, by which the
computing circuit can identify the object.
In the immediately following text, to simplify explanations it is assumed
that an object or a code plate always lies in a plane oriented essentially
orthogonally to the angle bisector of the angle of view. If the object or
code plate is oriented askew by a known angle to the angle bisector of the
angle of view, the distances calculated by the computing circuit from the
object or code plate to the optical center of the sensor device are to be
corrected by the sine of this angle.
If, in a line of machines for the automatic processing and of devices for
the automatic treatment of electronic chips, the mounting robot R is
provided with a sensor device of the type specified above, the computing
circuit supplies the information specifying the distance and position of
the machines B1-B4 and devices E1-E2, but only in the plane of the
scanning with the laser beam or orthogonally to the axis of the rotating
mirror. To automate the movements of the mounting robot R there is still
missing the information in the direction parallel to the axis of the
rotating mirror or orthogonally to the plane of the scanning with the
laser beam, since the information obtained with a sensor device of the
type specified above is only two-dimensional, which is inadequate for
automating the movements of the mounting robot R.
To overcome this inadequacy by combining two sensor devices of the type
specified above is complex and, furthermore, disruptive owing to the
restricted space around the mounting robot.
SUMMARY OF THE INVENTION
The object of the invention is to improve a sensor device of the type
specified above in such a way that a single sensor supplies
three-dimensional information which suffices in particular for automating
the movements of the robot.
With the sensor device according to the invention, a single scanning device
suffices for positioning the mounting robot with the aid of a code field
according to the invention and, if appropriate, also for reading
information in additional code fields.
The invention makes it possible on the one hand to make the computing
circuit establish from the machines or devices and from the magazines
their positions and dimensions simply and, if appropriate, in an
automatically proceeding operation in order for these to be passed on as
information to the control of the mounting robot. The mounting robot
learns the positions and dimensions of the machines or devices and
magazines simply and, if appropriate, in an automatically proceeding
operation. Thereafter, the various positions of magazines at the various
machines or devices can be moved automatically by the gripper and the
various magazines can be handled according to their type.
On the other hand, it is possible with the invention to provide on the
machines, devices and magazines, on the same or other code carriers,
additionally and in a predetermined position in relation to the code field
according to the invention further code fields, which supply information,
for example on the type of a machine, of a magazine and the like. Because
the mounting robot knows the positions of the additional code fields in
relation to the code field according to the invention, as soon as it has
learned the positions and dimensions of the machines or devices and
magazines it is possible for it also to bring the further code fields into
the angle of view of the scanning device in order to read their
information.
Each time positions are moved to by the gripper these positions can,
moreover, be checked automatically by comparison of the newly established
actual position with the stored set position. The result of this check can
be used for automatically correcting distance errors, which are
attributable, for example, to the great length of the series of machines
or devices, and displaced positions, which are caused, for example, by
unintended displacing of the machines or devices or by movements and
vibrations of the ground, the originally learned positions being
correspondingly adjusted. The result of the check can also be used for
detecting the absence of certain positions or items, if, for example, at a
position for magazine reception no place is ready for an additional
magazine or at a position for magazine discharging no magazine is ready.
Finally, objects which are not programmed in the control of the mounting
robot can be detected as such, which allows this control to avoid
collisions of the mounting robot with obstacles, such as displaced
magazines, hanging-down cables, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in more detail below with reference to the
attached drawings. Further advantages of the invention are also evident
from this description.
In the drawings:
FIG. 1 schematically shows in perspective a line of machines for the
automatic processing and/or of devices for the automatic treatment of
electronic chips according to the prior art; and
FIG. 2 shows in schematic side view, selected elements of the prior art
line shown in FIG. 1.
FIG. 3 shows a plan view or a retro-reflector with the bar code according
to the invention as a mask, for use with the known sensor device of the
type specified above;
FIG. 4 shows a geometrical diagram of the angle and length relationships of
bar code and light beam in the sensor device;
FIGS. 5a and 5b each show a geometrical diagram of the angle and length
relationships of boundary lines and surface areas in an intermediate field
with a diagonal line and two optically identical intermediate field
regions; and
FIGS. 6a and 6b each show a geometrical diagram of the angle and length
relationships of boundary lines and surface areas in an intermediate field
with two optically different intermediate field regions.
DETAILED DESCRIPTION
In FIG. 3, a retro-reflector 1, known per se and described, for example, in
the already cited Namco brochure, is represented in plan view onto its
essentially planar retro-reflecting surface. The retro-reflector 1 is part
of a sensor device, for example of the type described in the cited Namco
brochure. This sensor device is, for example, attached on a robot, such as
the mounting robot R represented in FIGS. 1 and 2.
In principle, instead of a retro-reflector, a surface scattering the light
in a suitable way, i.e retro-diffusion instead of retro-reflection, may
also be used, and, instead of a laser beam, a different type of light beam
may be used. Also, instead of a periodic scanning with laser light and a
mirror rotating about an optical center, a global scanning may be used
with light from a row of LEDs with use of a row of photodetectors.
Attached on the retro-reflecting surface of the retro-reflector 1 is an
essentially planar mask, which has at certain points opaque thick
bar-shaped lines 2 and opaque thin bar-shaped lines 3, and is transparent
at its other points. The mask is, for example, a photographic emulsion
coating on a glass plate, which for its part is laid over the
retro-reflecting surface. The mask may, however, also be painted directly
with coloring on the retro-reflecting surface of the retro-reflector 1. In
principle the glass plate may also be arranged in front of the
retro-reflecting surface. The opaque lines are advantageously black, in
order also to be better perceivable by the eye.
The retro-reflector 1 with the applied mask is arranged at a predetermined
point on the rear side of each machine and device of FIG. 1, for example
at the point S in FIG. 2, at a predetermined height above the ground. This
height is entered into the computing circuit of the robot as a
corresponding default value and is consequently known by the control of
the robot, so that it is possible for it to move the robot in such a way
that the retro-reflector 1 comes into the angle of view of the sensor
device.
Furthermore, the computing circuit of the robot is informed by a
corresponding default value where in the case of a certain type of
machines or devices the individual points of significance, in particular
the positions at which magazines are to be brought or picked up, are
located in relation to the retro-reflector 1. Thus, as soon as the
computing circuit of the robot becomes aware in the way explained below of
the position of the retro-reflector 1, it is possible for the control of
the robot to make the gripper move automatically to the positions
mentioned and to handle the various magazines in accordance with their
type.
On the retro-reflector 1, the combination of lines, such as the lines 2 and
3, form various bar codes, which can be scanned by the light beam of the
sensor device. For this purpose, the lines, as usual in the case of bar
codes, are divided into groups of lines each with a coded meaning in the
combination of lines, and each group of lines is arranged within virtual,
(i.e. not provided with an actual border) rectangular line group regions,
in order to form an information block.
In the exemplary embodiment of FIG. 3, four particular line group regions
6A, 6B, 6C, 6D together form a virtual (i.e. not provided with an actual
border) essentially rectangular code field. The retro-reflector 1 is
arranged on a machine or device of FIG. 1 in such a way that a center line
of the rectangular code field lies essentially parallel to a scanning
plane of the sensor device (the center line of a rectangle is generally a
geometrically well-defined term, but in the present design of the
invention not an actually existing line, for which reason the center line
mentioned has not been drawn in FIG. 3).
In the rectangular code field, each of the line group regions 6A, 6B, 6C,
6D itself forms a virtual (i.e. not provided with an actual border)
rectangular positioning field, to be precise in such a way that the
rectangles concerned, virtually bordering the groups of lines, are
identical. Moreover, the groups of lines are oriented in their rectangles
or line group regions 6A, 6B, 6C, 6D in such a way that in each case a
longer border of the rectangle or line group region, such as the border 7
or 12, is also a longer border of a line. Finally, the rectangles or line
group regions 6A, 6B, 6C, 6D are arranged with respect to one another in
such a way that their virtual (i.e. not represented by an actual line)
short sides are aligned congruently and their long sides lie parallel to
one another (incidently, the terms "long" and "short" refer to the
particular representation according to FIG. 3, but they may be
interchanged within the scope of the invention). Incidently, the code in a
positioning field respectively comprises a group of lines of at least two
rectangular lines and a rectangular interspace lying in between, the lines
and interspaces differing optically from one another, for example such as
light and dark, and their longitudinal direction running at right angles
to the center line of the code field over the entire extent of the latter.
The respectively neighboring rectangular positioning fields or line group
regions 6A and 6B, or 6B and 6C, or 6C and 6D, are arranged at the same
predetermined distances from one another, so that in between in each case
the same virtual (i.e. not provided with an actual border) rectangular
interfields 8AB, 8BC, 8CD are defined. The code field is thus filled
exactly by a sequence, alternating along the center line, positioning
fields 6A, 6B, 6C and 6D and interfields 8AB, 8BC, 8CD.
The positioning fields or line group regions 6A, 6B, 6C, 6D form a series.
Each group of lines is coded for the position of the line group region 6A,
6B, 6C, 6D concerning them in the series, preferably with a number from a
series of consecutive numerical values. In the exemplary embodiment
according to FIG. 3, the line group region 6A is coded by the number 0,
the line by group region 6B by the number 1, the line group region 6C by
the number 2 and the line group region 6D by the number 3. Altogether, the
code arranged in a positioning field thus corresponds to a position of
this positioning field in the code field, and this code comprises
positional information which can be evaluated by the scanning device and
specifies at which point the positioning field is located in a sequence
formed by the positioning fields along the center line, the successive
positions of the positioning field in the code field preferably being
expressed by consecutive numerical values.
Arranged in each of the rectangular interfields 8AB, 8BC, 8CD there is in
each case a diagonal line 9AB, 9BC, 9CD, which joins the mutually
diagonally opposite ends of mutually opposite borders of the neighboring
positioning fields or line group regions, as for example the diagonal line
9BC joins an end 10 of the border 7 of the line group region 6C with an
end 11 of the border 12 of the line group region 6B. The diagonal line
9AB, 9BC, 9CD represents in the respective interfield 8AB, 8BC, 8CD a
boundary line, obliquely intersecting the center line, between two surface
areas of the interfield. During the scanning of this boundary line by the
scanning device, the brightness contrast between the interfields and the
diagonal line produces in the scanning device a variation of the
illumination density, to be correct two rapidly succeeding opposed
variations of the illumination density, which permits a determination of
the viewing direction, which is explained in more detail below in
conjunction with FIG. 4.
The arrangement described above as an example, of four positioning fields
or line group regions 6A, 6B, 6C, 6D and three diagonal lines 9AB, 9BC,
9CD in the respective interfield 8AB, 8BC, 8CD, may readily be extended to
a higher, but preferably even number of line group regions and the
corresponding, one less, odd number of preferably mutually parallel
diagonal lines.
The diagonal lines 9AB, 9BC, 9CD, as represented in FIG. 3, are preferably
oriented parallel to one another, although this is not obligatory if the
computing circuit has the information necessary for further processing.
With regard to the description of the method according to the invention of
automatically positioning the robot with respect to the retro-reflector
with the mask lined thereupon, it is first of all expedient to explain the
geometrical diagram represented in FIG. 4 of the angle and length
relationships of bar code and light beam in the sensor device.
The basis taken for this (in particular because of the simpler geometrical
relationships) is the known scanning device, for example described in the
already cited Namco brochure. In principle, however, the periodic scanning
known from the latter with laser light and a mirror rotating about an
optical center could be replaced by a global scanning with light from a
row of LEDs with use of a row of photodetectors, without departing from
the principle of the explanations which follow.
In FIG. 4, a wall 40 of a machine or device on which the retro-reflector 41
is arranged is schematically represented. Arranged on the retro-reflector
41 is the mask 42, which bears the bar code, of which only a point 43 of a
diagonal line, such as the diagonal lines 9AB, 9BC or 9CD of FIG. 3, is
represented.
The light beam emanates from the point 44 and is sent back to the point 44
by the retro-reflector 41, unless this is prevented by the bar code of the
mask 42. The point 44 thus has in the diagram of FIG. 4 the significance
of an optical center of the sensor device. The retro-reflector 41 and the
mask 42 are represented in the diagram of FIG. 4 with a considerable
thickness, but this serves only that the retro-reflector 41 and the mask
42 can be seen and in the following is insignificant and need not be paid
any attention.
On account of the deflection of the light beam by the constantly rotating
mirror, the light beam moves continuously about the point 44, for example
in the clockwise sense. The angular positions of the light beam are
measured positively in the clockwise sense in FIG. 4, their zero value
lying at an angular position predetermined in the sensor device by the
angle-reference detector, which position is represented in FIG. 4 by the
reference direction 45. During the course of a rotational period of the
mirror, the angular position increases in the direction of the arrow 46
about the point 44 from a value at the beginning (not shown) of the angle
of view at a time t.sub.A, via a value at the beginning of the scanning of
the mask at the line 47 at a time t.sub.U and thereafter a value at the
end of the scanning of the mask at the line 48 at a time t.sub.V, up to a
value (not shown) at the end of the angle of view at a time t.sub.E. In
this case, the angular position coincides with the angle bisector of the
angle of view at a time t.sub.W which corresponds to the equation t.sub.M
=1/2(t.sub.E -t.sub.A). This operation is repeated with every revolution
of the constantly rotating mirror, which leads to periodic scanning of an
angle of view predetermined by the design of the sensor device.
As already mentioned, to simplify the explanations which follow it is
assumed that the retro-reflector 41 and the mask 42 lie in a plane
oriented essentially orthogonally to the angle bisector of the angle of
view. Consequently, the angle bisector of the angle of view coincides with
the normal 49 of the optical center 44 to the retro-reflector 41 and to
the mask 42.
Because the computing circuit of the robot is known as the corresponding
default value at which height above the ground the retro-reflector 41 is
located, it is possible for the control to move the robot in such a way
that the retro-reflector 41 comes into the angle of view of the sensor
device, and the photo-detector receives a retro-reflecting light beam when
the emanating light beam meets the retro-reflector 41. Once the
retro-reflector 41 has in this way come into the angle of view, the method
of automatically positioning a robot with the sensor device proceeds in
the following way.
In a first phase, the control of the robot receives from the computing
circuit the necessary information in order to set both the angular
position at the normal 49 and the length of the normal 49, that is to say
the distance from the optical center 44 to the retro-reflector 41, in such
a way that the angle of view covers all the line group regions of the
mask, that is to say in the case of the example according to FIG. 3, all
four line group regions 6A, 6B, 6C, 6D. In other words, it is in this case
achieved that the pulses of the photodetector, which correspond to the
lines of these groups of lines, all occur in the time interval between
t.sub.A and t.sub.E. An earliest pulse, which begins at the time t.sub.1A,
and a latest pulse, which stops at the time t.sub.1E, correspond to the
group of lines first scanned. An earliest pulse which begins at the time
t.sub.2A, and a latest pulse, which stops at the time t.sub.2E, correspond
to the group of lines last scanned.
How the operation continues in this first phase can be explained most
simply if the optical center 44 is brought in a first stage to the center
perpendicular of the overall length of the line group regions 6A, 6B, 6C,
6D and in a second stage as close as possible to the line group regions
6A, 6B, 6C, 6D.
For example, the robot is for this purpose moved initially only in the
horizontal until the time t.sub.M corresponds to the equation t.sub.M
=1/2(t.sub.2E -t.sub.1A), achieving the effect that the angle bisector of
the angle of view coincides with the center perpendicular of the overall
length of the line group regions, i.e. is congruent to it, and the optical
center 44 lies centered, initially only in the horizontal, in front of the
line group regions 6A, 6B, 6C, 6D. Thereafter, the robot is controlled,
still only in the horizontal, in such a way that the time t.sub.M
continues to correspond to the equation t.sub.M =1/2(t.sub.2E -t.sub.1A)
and, in addition, the times t.sub.1A and t.sub.2E come to correspond to
the equations t.sub.1A =t.sub.A and t.sub.2E =t.sub.E, then achieving the
effect that the overall length of the line group regions fills the entire
angle of view. Of course, the control receives the information necessary
for this continuously from the computing circuit.
In a second phase, the control receives from the computing circuit the
information necessary to reduce the distance between the optical center 44
and the retro-reflector 41, that is to say the length of the normal 49, in
such a way that the angle of view from then on covers only two neighboring
line group regions. Which regions these two neighboring line group regions
are is selected on the basis of the coding of their groups of lines and a
corresponding default value in the control. They are expediently
neighboring line group regions in the center of the series, that is to say
in the case of the example according to FIG. 3, the line group regions 6B
and 6C, which are coded by the numbers 2 and 3, respectively, which are
detected by the computing circuit. Of course, the optical center 44 in
this case remains centered in the horizontal in front of the line group
regions 6A, 6B, 6C, 6D.
With this approaching of the retro-reflector by the robot it is essentially
intended to increase the angular values at which the various bar codes of
the mask 42 are seen from the optical center 44, and thereby increase the
precision of the positioning. From then on, the only diagonal line lying
in the angle of view is the diagonal line 9BC, of which a point 43 is
represented in FIG. 4
In a third phase, the control receives from the computing circuit the
information necessary to move the robot, in this case only in the
vertical, until the time at which the angular position of the light beam
coincides with the point 43 of the diagonal line 9BC, or the point 43 is
scanned, which coincides with the time t.sub.M, achieving the effect that
the optical center 44 is then also centered in the vertical in front of
the line group regions 6B, 6C. During this time, the robot has not been
moved in the horizontal, so that the angle of view continues to be covered
only by the neighboring line group regions 6B and 6C and the optical
center 44 has remained centered in the horizontal in front of the line
group regions 6A, 6B, 6C, 6D.
Consequently, the optical center 44 now lies centered in the horizontal and
in the vertical in front of the line group regions 6A, 6B, 6C, 6D.
The computing circuit is thereupon in the position to calculate the
coordinates of the optical center 44 with respect to the center point of
the line group regions 6A, 6B, 6C, 6D. In Cartesian coordinates, the
coordinate in the direction perpendicular to the retro-reflector 41 and to
the mask 42 is given by the length of the normal 49, while in the
directions parallel to the retro-reflector 41 and to the mask 42 the
coordinate is equal to zero, because the optical center 44 is indeed
centered in front of the line group regions 6A, 6B, 6C, 6D (this is the
very simplification mentioned above). These coordinates, or the individual
coordinate actually to be determined are prepared by the computing circuit
for use by the control as a position reference of the robot with respect
to the retro-reflector and are passed to the control. From then on, the
control of the robot is capable of making the gripper move automatically
to the individual points of significance at the machine or device
concerned, in particular the positions at which magazines are to be
brought or picked up, and handle the various magazines in accordance with
their type.
In general, there are two mutually equivalent possibilities of relating the
local reference systems of the code carrier and of the scanning device to
each other, namely by creating a direct relationship or an indirect
relationship by means of a common system of coordinates or more than one
system of coordinates related to one another. On the one hand, in the
scanning plane the angular position of the viewing direction about the
optical center may be related to a reference direction lying in a
predetermined angular position to the plane of the code carrier. On the
other hand, the plane of the code carrier may be arranged in a position
predetermined in a system of coordinates, while in the scanning plane the
angular position of the viewing direction about the optical center is
related to a reference direction of the angular position predetermined in
the system of coordinates.
Preferably, however, all the calculations are simplified by the reference
direction lying orthogonally to the plane of the code carrier and the
displacements taking place in three mutually orthogonal directions, of
which one lies parallel to the reference direction and the two others lie
parallel to the plane of the code carrier.
For executing the method according to the invention, it would suffice for
the line group regions to lie in the angle of view, while, in principle,
it is not necessary for the angle bisector of the angle of view to
coincide with the center perpendicular of the line group regions. If the
angle bisector of the angle of view does not coincide with the center
perpendicular of the line group regions, the optical center of the sensor
device is not centered in front of the line group regions, whereupon the
trigonometric calculation of the position of the optical center in
relation to the retro-reflector becomes more complicated and the computing
circuit and the control become correspondingly more complex, but the
calculation and the corresponding design of the computing circuit and of
the control remain within the scope of general technical knowledge and
therefore need not be described in detail. For example, the computing
circuit may be designed as a microprocessor and be correspondingly
programmed.
For executing the method according to the invention, it would also suffice
for the overall length of the line group regions to fill the entire angle
of view, while it is not necessary for only two selected line group
regions to fill the entire angle of view. If no approaching of the sensor
device to the retro-reflector takes place, the only effect is that the
achieved precision of the position determination in the horizontal and in
the vertical as well is less than in the case of the method described with
such an approach.
Finally, for executing the method according to the invention it is not
essential for the optical center 44 also to be centered in the vertical in
front of the line group regions 6B, 6C. In general, the angular position
of the light beam at a certain time t.sub.H coincides with the diagonal
line 9BC, i.e. a point 43 of the diagonal line 9C is scanned at the time
t.sub.H. This time t.sub.H varies linearly with the position of the
optical center 44 ill the vertical in front of the line group regions 6B,
6C. It is assumed that the optical center 44 is centered in the horizontal
in front of the line group regions 6B, 6C, as described in the text above,
that is to say that the equation t.sub.M =1/2(t.sub.2E -t.sub.1A) is
satisfied. Under these circumstances, the time t.sub.H coincides with the
time t.sub.M when the optical center 44 is also centered in the vertical
in front of the line group regions 6B, 6C. However, the time t.sub.H
coincides with the time t.sub.1E when the optical center 44 lies in the
vertical in front of the border last scanned of the group of lines first
scanned, and coincides with the time t.sub.2A when the optical center 44
lies in the horizontal in front of the border first scanned of the group
of lines last scanned. Consequently, this time t.sub.H varies linearly
between the extreme values t.sub.1E and t.sub.2A in dependence on the
position of the optical center 44, in the vertical in front of the line
group regions 6B, 6C. A simple proportional calculation thus allows the
computing circuit to calculate the position of the optical center 44 in
the vertical in front of the line group regions 6B, 6C in dependence on
the times t.sub.H, t.sub.1E and t.sub.2A and to prepare it for use by the
control of the robot.
The preparation described of the information on the position of the optical
center of the sensor device in the horizontal and in the vertical in front
of the line group regions, that is to say in front of the retro-reflector
and the mask, and the passing on of this information to the computing
circuit makes it possible for the control of the robot to position itself,
if appropriate, in front of other line group regions, such as for example
in front of the line group regions 4 or 5 in FIG. 3, in order to read
further information in these additional code fields. For example, the type
of the machine or device on which the retro-reflector 1 is attached is
coded on the retro-reflector 1 in the line group region 4, while a further
line group region 5 can be used for additional coded information.
Moreover, one or more further retro-reflectors may be provided with
additional code fields and be arranged ill a predetermined position in
relation to the retro-reflector 1. Since the computing circuit is aware of
the predetermined position of these additional code fields in relation to
the code field of the retro-reflector 1, it is possible for the control of
the robot to go to these additional code fields without a preceding
search, in order to read their information.
Consequently, a single scanning device suffices both for the initially
necessary determination of the position of the mounting robot ill relation
to the machines or devices and their magazine positions and thereafter for
the reading of further code fields, which supply information, for example,
on the type of a machine, of a magazine and the like. Because the mounting
robot knows the positions of the additional code fields as soon as it has
learned the positions and dimensions on the machines or devices and on the
magazines, it is possible for it also to move to the further code fields
and bring itself into the angle of view of the scanning device, in order
to read their information.
By the preparation described of the information on the position of the
optical center of the sensor device in the horizontal and in the vertical
ill front of the line group regions, that is to say in front of the
retro-reflector and the mask, and by the passing on of this information to
the control of a robot, it is possible, for example, to control a mounting
robot for a line of machines and/or devices, in particular for the
automatic processing, and/or of devices for the automatic treatment of
electronic chips in such a way that the correct magazines are brought to
the correct position of the correct machines or devices and are picked up
from these positions.
In the case of any one of these positioning operations, the computing
circuit of the sensor device and/or the control may also check whether the
current set position coincides with the set position determined earlier.
If this is not the case, the machine and/or device concerned has, for
example, been displaced or otherwise changed, which, for example, sets off
an alarm.
In FIGS. 5a, 5b, 6a and 6b, in each case various variants of the design of
the code in an interfield are represented as a geometrical diagram. The
frame now represented diagrammatically corresponds in each case to the
interfield which has already been described in the above text in
conjunction with FIG. 3, but there only with a virtual border, i.e. not
represented by an actual line.
In FIG. 5a, for a better overview, the design which has already been
described in the text above in conjunction with FIG. 3 is represented once
again. A diagonal line crosses through the interfield, essentially
diagonally and by section approximately into two interfield regions of an
optically identical nature. The diagonal line is dark and the interfield
regions are light (or vice versa), i.e. the diagonal line is optically
different from the interfield regions. Each of the two interfield regions
produces with the diagonal line a boundary line, which crosses through the
interfield approximately diagonally; there are consequently two mutually
parallel boundary lines. The scanning device responds to the optical
contrast at the two boundary lines by this contrast producing in it a
variation of the illumination density, which leads to the determination of
a viewing direction.
In FIG. 5b, a design which is derived from the design according to FIG. 5a
essentially by mirror-symmetrical duplication is represented, the
interfield being essentially bisected along the center line into two
interfield parts, and the diagonal lines of one interfield part and of the
other interfield part lying at an angle to each other so as to be
chevron-shaped.
In FIG. 6a, a design in which the interfield is essentially bisected
essentially diagonally into two optically different interfield regions is
represented. The one interfield region is dark and the other light, i.e. a
boundary line crosses through the interfield essentially diagonally. The
scanning device responds to the optical contrast at this boundary line by
this contrast producing in it a variation of the illumination density,
which leads to the determination of a viewing direction.
In FIG. 6b, a design which is derived from the design according to FIG. 6a
essentially by mirror-symmetrical duplication is represented, the
interfield being essentially bisected along the center line into two
interfield parts and the boundary lines of one interfield part and of the
other interfield part lying at an angle to each other as to be
chevron-shaped.
It is quite possible for there to be other designs of the code in an
interfield, in which the code in at least one interfield comprises at
least one a boundary line obliquely intersecting the center line between
two surface areas of the interfield, and the surface areas are designed
for the purpose of producing during the scanning of their common boundary
line by the scanning device in the latter a variation of the illumination
density, which leads to the determination of a viewing direction. In
particular, it is to be understood that the drawings represented in FIGS.
5a, 5b, 6a and 6b can be mirror-inverted about the two virtual center
lines of their rectangles, i.e. in FIGS. 5a, 5b, 6a and 6b the terms
"upper" and "lower" are interchangeable, and likewise the terms "light"
and "dark" are interchangeable, without departing from the principle of
the invention.
In all the designs of the code described in the above text, the code field
preferably comprises an even number of positioning fields of the same size
as one another and a corresponding odd number, one less, of interfields of
different sizes to one another, and the interfields are either identical
or mirror-identical to one another. In the preferred design according to
FIG. 3 the code field comprises precisely four positioning fields and
three interfields.
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